linux-kernel - Re: [PATCH v6 20/20] modpost: show offset from symbol for section mismatch warnings

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Message-ID: <CAK7LNAQrzN2HR30rNM1Vx0S37X3t2b5rxELC=AVixQKrWu8y_w@mail.gmail.com>
Date:   Sun, 28 May 2023 16:29:42 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nicolas Schier <nicolas@...sle.eu>
Subject: Re: [PATCH v6 20/20] modpost: show offset from symbol for section
 mismatch warnings

On Fri, May 26, 2023 at 3:27 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Sun, May 21, 2023 at 9:05 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> >
> > Currently, modpost only shows the symbol names and section names, so it
> > repeats the same message if there are multiple relocations in the same
> > symbol. It is common the relocation spans across multiple instructions.
> >
> > It is better to show the offset from the symbol.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > ---
> >
> >  scripts/mod/modpost.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > index e7561fa57478..4da96746a03b 100644
> > --- a/scripts/mod/modpost.c
> > +++ b/scripts/mod/modpost.c
> > @@ -1135,8 +1135,8 @@ static void default_mismatch_handler(const char *modname, struct elf_info *elf,
> >
> >         sec_mismatch_count++;
> >
> > -       warn("%s: section mismatch in reference: %s (section: %s) -> %s (section: %s)\n",
> > -            modname, fromsym, fromsec, tosym, tosec);
> > +       warn("%s: section mismatch in reference: %s+0x%x (section: %s) -> %s (section: %s)\n",
> > +            modname, fromsym, (unsigned int)(faddr - from->st_value), fromsec, tosym, tosec);
>
> Is the cast necessary if you use the %p format specifier instead of 0x%x?

No.

faddr and from->st_value are offsets from
the start of the section. They are not pointers.

%p does not make sense.






>
> >
> >         if (mismatch->mismatch == EXTABLE_TO_NON_TEXT) {
> >                 if (match(tosec, mismatch->bad_tosec))
> > --
> > 2.39.2
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers



-- 
Best Regards
Masahiro Yamada